In the manufacture of aircraft fuselages it is sometimes desirable to join together relatively thin components of non-weldable materials, such as joining non-weldable metal stringers to non-weldable skin. 2XXX aluminum alloys are used in the aircraft industry for their high tolerance to damage, and 7XXX and/or aluminum-lithium alloys are used for their high strength. Currently, joining 2XXX to 2XXX, 2XXX to 7XXX, or 7XXX to 7XXX alloys requires riveting them together, which takes time, adds weight, can cause surface deformities and other defects, and reduces performance in compression.
There are a limited number of techniques for joining non-weldable aluminum alloys, but most such techniques produce a material with varying properties. Ultrasonic joining can produce a near-zero metallurgical effect, and can join continuously, but is only suitable for joining thin (<0.04 inches) sheets. Further, ultrasonic joining produces a gnarled surface which can lead to stress concentrators. Linear friction and friction stir joining can produce a reduced or even near-zero metallurgical effect, but are limited to batch-type processes and relatively stiff materials. Magnetic pulse joining can produce a near-zero metallurgical effect, but is also limited to batch-type processes and is not as technology-ready as ultrasonic joining. Explosive joining can produce too much heat for use with relatively thin pieces used in many applications (e.g., components of aircraft fuselages). All of these are considered to be solid-state welding techniques.
There are more techniques available for welding weldable aluminum alloys. Arc, plasma, MIG, and TIG welding are conventional techniques for joining weldable aluminum alloys. Laser beam welding is a relatively old technology with new economic capabilities due to reductions in laser costs and improvements in automation. All of these are considered to be fusion-based welding techniques.
This background discussion is intended to provide information related to the present invention which is not necessarily prior art.